Safety switch for portable appliances



Nov. 13, 1951 D. c. GERBER SAFETY SWITCH FOR PORTABLE APPLIANCES INVENTOH. flaw 6. Gerber I5 Sheets-Sheet 1 Filed June 14, 1949 ATTONEY.

Nov. 13, 1951 11c. GERBER SAFETY SWITCH FOR PORTABLE APPLIANCES 3 Sheets-Sheet 2 Filed June 14, 1949 a I 5 Z Z 7 I imi- IIIIIII Fzlg. 3

INVENTOH. Dae (Z 6et'her BY WSW ATTORNEY.

Fig. 4

New, 13, 1951 D. c. GERBER SAFETY SWITCH FOR PORTABLE APPLIANCES 3 Sheet 3 Filed Jun 1 949 INVENTOR. Date a Gefbgr ATTOHN EY Patented Nov. 13, 1951 SAFETY SWITCH FOR PORTABLE APPLIANCES Dale G. Gerber, North Canton, Ohio, asslgnor to The Hoover Company, North Canton, Qhio, a

corporation of Ohio Application June 14, 1949, Serial No. 98,958

12 Claims.

This invention relates to portable power appliances and more particularly to a safety switch for such appliances designed to prevent accidental energization by connecting the service cord into a wall receptacle.

Many portable power driven devices are dangerous or likely to damage adjacent objects or the device itself if inadvertently energized when the operator is not present. While many examples of such devices, such as portable saws, grinders, drills, etc., might be cited, as here disclosed, the invention is applied t a floor polisher which serves unusually well to illustrate the utility and advantages of my novel safety switch. Thus, a floor polisher belongs to that category of portable tools which normally rest upon the motor driven polishing brushes. If it is energized in the absence of the operator, the polisher will move about the floor with the likelihood of damaging furniture in the room, upsetting and breaking objects on. tables and possibly injuring the polisher itself. Locating an electric switch on the appliance is an inadequate safeguard since the operator may leave the switch in the on position when last using the appliance. Connection of the service plug to the power source energizes the polisher which may start moving about the floor causing considerable damage before the operator can reach its handle.

Dead man types of switches are in general use to insure against inadvertent energization of portable devices. But these are objectionable for many reasons chief among which is that the operator must maintain a firm and continuous grip on the dead man control as long as the appliance is in use. This is irksome and an inconvenience entirely overcome by this invention.

The present invention provides a safety switch which is automatic in its operation, which requires no attention from the operator and which remembers to open the switch when the operator forgets to do so. Under no circumstances can the appliance be energized by connecting the service plug to a power source. It is inexpensive, si ple in construction, fool-proof and positive in operation. These ends are accomplished by utilizing energy from the magnetic field of the driving motor to hold the switch in closed position. Should the motor be tie-energized, the magnetic field collapses and the switch opens and remains open until manually closed by the operator.

It is an object of the invention to provide a novel safety switch for appliances which automatically opens upon a power failure or interruption for any reason.

Another object is the provision of a safety switch requiring the presence and deliberation action of the operator before the switch can be closed after the power has been cut off or fails.

A still further object is the provision on a portable appliance of a new safety device for controlling the power supply which is operable to energize or de-energize the appliance merely by pressing a button.

These and other objects will become apparent from the following description and drawings 01' two illustrative embodiments of the invention.

Figure 1 is a view of a floor polisher incorporating the invention;

Figure 2 is an isometric view of one embodiment of the safety switch;

Figure 3 is a vertical sectional view of a push push switch forming a sub-assembly of the com plete safety switch;

Figure 4 is a plan view of the operating slide for the push-push switch;

Figure 5 is a fragmentary view of a second embodiment showing the switch in closed position; and

Figure 6 is a view of the same switch in open position.

Referring to the drawings, the invention is shown as applied to a floor polisher Hi having an operating handle with a bail H pivoted t the opposite ends of the polisher. An electric motor and driving gears housed within the main casing are connected in well known manner'to drive a pair of oppositely rotating polishing brushes |2l2. The safety switch incorporating the present invention is shown as mounted on the lower rear side of the polisher frame. The only part of the switch which can be seen in Figure l is the foot operating pedal i3. This pedal is de pressed about a pivot within the main housing to open or close the switch.

The safety switch proper is shown in Figure 2. As will be seen from this view the operating pedal l 3 is carried by a generally U -shaped stamping it pivotally connected at l5 to the sides of a second upstanding U-bracket l6. Portion H of bracket I6 is secured to the main frame 18 of the floor polisher. Carried by the upward forward corner of bracket I 4 is a rod I 9 which rotates downwardly about pivot I5 when the foot pedal I3 is depressed and in so doing operates a push-push switch 28.

Push-push switch 20 may be of any well known construction modified as necessary and as hereinafter described to make provision for the present invention. The switch includes a housing 2! of insulation material and a molded cover held to the main body by rivets 23-23. The main body houses a conventional snap-action toggle mechanism 24 pivotally supported in recesses in the opposite side of housing 2|. The switch terminals are not illustrated but will be understood to be of any well known type. The switch is of the type ported on shaft 28 and provides a support'for a compression spring 30. The other end ofthespring bears against the lower side of a retainer 23 for a floating switch operator pin 3! which in turn bears against plunger 26. Thus, it will be evident that spring 30 urges plunger 26 to its uppermost position except when it is manually depressed. When plunger 26 is depressed, .it will be apparent that the lower end of operating pin 2| contacts the cam surface 32 of pintle 21 causing it to rotate slightly in one direction or the other to operate toggle mechanism 24.

Reference will now be had to the mechanism for holding switch closedso long as the motor is energized and for immediately opening the switch should the motor be dc-energized for any reason. The motor field stack is indicated at 35 of Figure 2. This stack comprises U-shaped laminations with a field coil mounted on its bight portion. The spaced apart legs of the laminations accommodate the motor armature and form the poles of the motor at diametrically opposed sides of the armature. A plate-like armature 38 Y of soft iron or the like is pivotally mounted at its upper end on a cross-rod 31 carried by the upper ends of bracket l6. This plate forms an armature which when pivoted toward the field stack 35 contacts and bridges the spaced apart ends of field stack 35. Bell crank 38 is pivotally mounted on bracket it. One end of this bell crank underlies a tab '35 secured to armature plate 36 while the other lower end of the bell crank extends through an opening 34 formed in the outer end of slide member 40 housed within guideways formed in cover 22 of the push-push switch. Slide 40 has the general shape indicated in Figure 4. and is so constructed as to have limited reciprocal motion through an end of cover 22.

Referring to Figure 3, it will be seen that pintle 21 extends downwardly through an opening 4i in slide 40. Opening 4| is large enough to receive the pintle and to permit the limited rocking movement of the pintle as the slide occupies its various positions. One end of a rather stifi leaf spring 42 is secured to the switch housing while the op-' posite upturned end projects through an opening 43 in slide 40. Spring 42 urges slide 40 toward the switch housing so that the switch parts occupy the position shown in Figure 3 wherein the switch is open. This is also the position of the d. necting bar It downwardly to depress plunger 28 of the push-push switch 28. As a result, the lower end of pin 3i strikes the left side-oi cam surface 32 on pintle 2? and retains it counterclockwise to snap the toggle mechanism as to the left to close the switch. Movement of pintle 27 operates to move slide id to the right against the action of spring d2. Movement of slide it to the right also rotates bell crank 38 counterclockwise allowing armature 38 to rotate against the ends of the field stack pole faces. Movement of the armature is facilitated by the magnetic flux flowing in the field stack. The magnetic field holds armature 36 tightly against. the pole faces with sumcient force to overcome the stress of spring 42. Meanwhile the operator will, of course, have hold of the floor polisher handle with which he can direct the polisher as desired in the use of the polisher.-

If it is desired to discontinue use of the polisher, the operator merely steps upon. pedal it to again depress plunger 26. The end of pin 35 now operates upon the other or the right-hand side of cam 32 on pintle 21 so as to move the toggle'mechanism 24 to its open switch position. At the'same time, slide 40 will bemoved to the left pivoting armature 35 awa from the motor "field stack. The polisher can be re-energized and de-energized as often as desired by stepping on the foot pedal to either start or stop the motor.

However, let us assume that the power supply suddenl fails while the operator is using the polisher and that he forgets to open the switch before leaving the polisher to seek the cause of the power failure. While on this errand, the power supply may resume. But without his knowledge or any action on his part the switch has opened automatically and resumption or power suddenly and in the absence of the opera-=- tor can result in no harm. This is for the reason that immediately upon occurrence of the power failure, the magnetic field of the motor collapsed allowing spring 42 to take control of slide $8 and urge it into the switch housing. This movement causes pintle 21 to be moved to the left moving toggle mechanism 26 to the open position of the switch. The only way in which the polisher may be re-energized upon resumption of the power supply is for the operator to manually depress the foot pedal E3 to close the switch and reset the safety mechanism.

' A second embodiment of the invention is illustrated in Figures 5 and 6. Thesame or similar component elements are designated by the same reference numerals as in the first embodiment distinguished by a prime mark. Thus the push= .push switch 20' is essentially identical-to switch 20. This switch is mounted upon an angle bracket 50 secured to the polisher frame I8. oppositely facing tabs 5! struck from member. 50 provide a raceway for slide member "the upper inturned end 53 of which overlies the top parts as illustrated in Figure 2. Thus, as there shown, armature I6 is pivoted outwardly away from the pole faces and the bell crank 38 is pivoted to its furthest clockwise extent.

Operation of the switch plunger 26'. The lower end of slide 52 interlocks with the lever 54 pivoted to the under side of the polisher frame at B8. The

outer end of lever 54 carries foot pedal 18'. Lever 54 is spring biased upwardly so as to hold slide member 52 in its uppermost position normally,

The armature plate 36' constituting apart of the safety mechanism is carried by bracket 86 pivoted on vertical spindle 51 which is secured to mounting bracket 50. A tension spring :58 extends between an arm of bracket 56 and a part of the motor frame in such manner as to pivot tha armature-38' away from-the motor held stack It will be noted that the connection of spring 58 to bracket is such that the spring has little or very limited effect on the armature 35 when the latter is pivoted into bridging contact with the motor poles. However, when the armature is pivoted away from the poles, spring El has a maximum pivoting efiect on thearmature mounting bracket 56. An extension 59 of bracket 56 limits movement of the armature away from the pole faces by contacting either bracket 50 or some part of polisher frame ll.

Bell crank Bil is vertically pivoted to bracket so by pin 6!. An inturned tab 82 on the'upper arm of the bell crank is positioned to interact with an out-turned tab 63 on the outer end of the switch slide M. It will be noted that the upper end of bell crank is interconnected with the pivoted armature bracket 56 by a link GI. Accordingly, it will be clear that spring 5E acts to pivot bell crank 50 clockwise and to urge slide dd toward its outermost position and away from the push-push switch housing.

A cammed surface or notch formed in the vertical edge of slide member 52 coacts with the cammed lower end 66 of bell crank Bil. It will, therefore, be evident that downward movement of slide 52 acts through cams 65 and 58 to rotate bell crank so counterclockwise. This movement causes armature 36' to be pivoted into bridging contact with the pole faces of the motor stack and to increase the stress on spring 58. At the same time, downward movement of slide 52 causes the inturned end 53 to depress plunger 25' of the push-mush switch. The relative position of the parts when the switch is in closed position is illustrated in Figure 5, while Figure 6 shows the position of the parts with the switch open.

Operation toggle mechanism closes the switch to the motor.

Counterclockwise movement of the bell crank also stresses tension spring 58 and moves armature 35 against the end of the motor poles. Immediately upon energization of the motor, the magnetic field thereby established holds the armature tightly in contact with the pole faces. 'As will be evident from Figure 5, with the motor energized, the line of action of spring 58 passes closely adjacent to the axis of pivot pin 51 for the armature. Accordingly, the spring is relatively ineffective to pivot the armature away from the motor field.

If it is desired to discontinue the operation of the polisher, the operator merely steps on pedal it to again depress plunger 26' thereby snapping the toggle switch to its open position. Movement of the foot pedal to open the switch does not disturb bell crank 60 nor the position of the armature due to the lost motion connection between tabs 62 and 63. However, deenergization of the motor results in the collapse of the magnetic field thereby allowing spring 5' to move armature 36' away from the motor stack.

If the power supply should fail, the magnetic field of the motor will collapse and spring 58 will pivot the armature away ifrcm the field stack. As the armature pivots, spring 58 becomes more and more efl'ective and supplies the energy required to snap slide 40' briskly toward its outer most position and to operate the toggle mechanism to open the switch.

From the foregoing it will be obvious that the present invention provides an unusually simple yet highly eiiective and satisfactory safety switch having numerous advantages over devices heretoiore known. The operator merely depresses a button to either close or open the switch. No other or different operations are ever necessary under any conditions of use. If the operator forgets or fails to open the switch after a period of use or after a power failure, this mechanism remembers'and opens the switch at the moment of power failure or at the instant the service plug is detached.

While only two embodiments of the invention have been disclosed it will be obvious that it may take numerous other forms without departing from the spirit of the invention. For example. other types of switches may be employed as can various linkages and arrangements for opening the'switch upon a failure of power to. the motor.

It is to be understood that the protection herein applied for is not confined to the particular I combinations of features or elements set out in the following claims. Protection is herein applied for for any one or more of the features or elements referred to in the following claims, or described in the foregoing specification or shown in the accompanying drawings, either independently or in combination.

I claim:

1. The combination with a motor-driven floor polisher, of a safety switch therefor comprising a manually operable switch having an open position and a closed position, a movable armature coupled thereto arranged to be moved to a position to bridge a gap in a magnetic flux circuit of said motor simultaneously with the closing of said'switch and to be moved away from said gap as said switch is opened, and means biasing said switch to open position but inefiective to do so while the magnetic field of said motor holds said armature whereby, upon failure of the power supply. the collapse of the magnetic field releases said armature allowing said biasing means to open said switch.

2. The combination defined in the preceding cla'im'in which said switch is of the push-push type which operates to open and close the motor circuit upon successive uni-directional movement oi said manually operable means and in which the manual means for said switch includes a lever extending outwardly from said polisher operable when depressed successively to open said switch on one depression and close it on the next depression and to reset said movable armature automatically to bridge a gap in a magnetic flux circuit-of said motor field each time the switch is closed.

3. The combination with a portable powerdriven appliance having a driving motor, of a safety switch therefor comprising a push-push switch, a foot operated lever operable to depress said switch to open or to close the same, spring means including a pivoted lever arm coupled to said switch operable to open said switch and including means having an armature which is moved into close magnetic coupling with said moviailure. I '5 7. The combination with a portable appliance inc-races 8 movable into and away item the magnetic field. oi said motor, means biasing said armature away irom said motor, and means connecting-said artor and 'to' open the switch upon interruption or the power supply to the appliance; 4. The combination defined in; the preceding claim characterized in that theeffectivelever arm on said spring islesswhen saidiswitch closed than when the switch is'open.

- s. The combination with aportable appliance having anrelectric driving motorpot a safety switch for controlling the energizationoi :said

motor, said switch including a'manually' oper-g able member to close said switch, anarmature coupled to said switch and movable by andupon closure 01 said switch into close coupling with the magnetic field of said motor, means biasing said switch toward open position but ineflective the magnetic field on said armature, said biasing means being operable to open said switch immediately .upon the collapse of said magnetic field' to open said switch against the holding action of to move said armature out or close coupling with the magnetic field of said motor upon power having an electric driving motor, 0! -a,safety switch ior said motor carried by said appliance,

manually operable means ior opening-and closing said switch to controlthe operation of-sahl motor, and pivoted lever means including a-spring and a movable armature subject to themagnetic field of said motor for automatically opening said switch without the interventionnoI-the operator upon an interruption of the powensupplylto said appliance, said spring being eflective to hold said switch open until manually closed upon re-establishment of the power supply to said. appliance, and said spring being so coupled to said lever means as to have a short efiective lever arm on said armature when said switch isxclosed and a relatively long effective lever arm .on said armature when said switch is open whereby a magnetic field. iorce adequate to hold said armature under close magnetic coupling conditionsis inadequate to move said armature against the action of said spring under loose magnetic coupling conditions.

8. The combination with a power-driven appliance oi the type supported in part when operating by a driven element thereof, of a safety switch carried by said appliance for controlling the driving motor therefor, manu lly operable means for opening and closing said switch, mag netically energizedspring' biased means operableto open said switch upon an interruption in the power supply, said last named means being-positioned to be energized solely from themagnetic ...field of said appliance motor and being movable I into close magnetic coupling with said motor 'au-.

tomatically when said switch is manually closed,

and being movable out of close magnetic couplingto said motor under the influence ot-said spring biased means when said switch is moved to. open positions- 9. A safety switch for use with an electric/n otor comprising a snap action toggle switch connected in circuitwith said notor, an armature magnetic held of the motor.

10. A safety switch comprising an insulated housing, a snap-action toggle mechanism pivotally'supported within said housing having two 'stable positions in one of which said switch is closed and in the other of which said switch is open, manually operable means mounted on said housing and operable to move said toggle mechanisnrirom one to the other oi said stable positions, and separate means extending from said toggle mechanism to a point exteriorly of said housing also operable to move said toggle mechanism from one stable position to the other, said toggle operating means including means biasing said toggle mechanism to-a particular one of its two stable positions.

- '11. The combination with a portable appliance having a housing enclosing an electric driving motor, an operating handleand at least one power tool operativcly connected to said motor so as to be driven thereby, of a safety switch device for controlling the supply of electric energy to said motor, said switch device being mounted in said housing and comprising a push-push switch having a "manually operated control member extending to an operating point exteriorly of said housing, an armature supported for movement between'a first position out of effective magnetic coupling with said motor and a second position wherein the magnetic coupling of the said motor therewith holds said armature captive, rigid switch operating means interconnecting said armature and said switch arranged so that said armature is in said first position when the switch is in open position and is in said second position when said switch is in closed position, and spring means operable to open said switch upon a power failure to said motor but inoperable by itself to open said switch against the holding action of said armature when said motor is energized.

12. The combination with a fioor polisher having a housing enclosing an electric driving motor, a propelling handle and at least one rotatin brush operatively connected to said motor so as to be driven thereby, of a safety switchdev ice for controlling the supply of electric energy to said motor, said device being mounted in s'aidhousing and comprising a switch movable between open and closed positions, a foot operated control member extending to a point exteriorly of said housing for opening and closing said switch, an armature supported for movement between a first and a second position, said first position being out of effective magnetic coupling with said motor and said second position being in such. close magnetic coupling with said motor that said armature is held captive so long as the motor is energized, rigid means connecting said armature and said switch for moving said armature between said first andsecond positions as said'switch is opened or closed, and spring means operable to open said switch and move said armature to said second position upon a power failure to said motor where- 9 10 by said polisher is not re-energized upon a resto- UNITED STATES PATENTS ration of the power supply to saidmotor. Number Name Date 1 I 1 DALE GERBER 7 528,430 Bartel Oct. 30, 1894 938,501 McBerty Nov. 2, 1909 REFERENCES CITED 5 1,751,781 Weiss Mar. 25, 1930 The followingreferences are of record ln the 2,073,244 Lotgren Mar. 9, 1937 file 0! this patent: 2,257,033 Blasell Sept. 23,194].

2,389,220 Tlfedeau Nov. 20, 1945 

